On 30.05.19 г. 19:31 ч., David Sterba wrote:
> The spinning_writers is either 0 or 1 and always updated under the lock,
> so we don't need the atomic_t semantics.
>
> Signed-off-by: David Sterba <dste...@suse.com>
> ---
> fs/btrfs/extent_io.c | 2 +-
> fs/btrfs/extent_io.h | 2 +-
> fs/btrfs/locking.c | 10 +++++-----
> fs/btrfs/print-tree.c | 2 +-
> 4 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 57b6de9df7c4..71ee9e976307 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4842,7 +4842,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info,
> u64 start,
> BUG_ON(len > MAX_INLINE_EXTENT_BUFFER_SIZE);
>
> #ifdef CONFIG_BTRFS_DEBUG
> - atomic_set(&eb->spinning_writers, 0);
> + eb->spinning_writers = 0;
> atomic_set(&eb->spinning_readers, 0);
> atomic_set(&eb->read_locks, 0);
> atomic_set(&eb->write_locks, 0);
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index 201da61dfc21..5616b96c365d 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -187,7 +187,7 @@ struct extent_buffer {
> wait_queue_head_t read_lock_wq;
> struct page *pages[INLINE_EXTENT_BUFFER_PAGES];
> #ifdef CONFIG_BTRFS_DEBUG
> - atomic_t spinning_writers;
> + int spinning_writers;
> atomic_t spinning_readers;
> atomic_t read_locks;
> atomic_t write_locks;
> diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
> index 5feb01147e19..270667627977 100644
> --- a/fs/btrfs/locking.c
> +++ b/fs/btrfs/locking.c
> @@ -15,19 +15,19 @@
> #ifdef CONFIG_BTRFS_DEBUG
> static void btrfs_assert_spinning_writers_get(struct extent_buffer *eb)
> {
> - WARN_ON(atomic_read(&eb->spinning_writers));
> - atomic_inc(&eb->spinning_writers);
> + WARN_ON(eb->spinning_writers);
> + eb->spinning_writers++;
> }
>
> static void btrfs_assert_spinning_writers_put(struct extent_buffer *eb)
> {
> - WARN_ON(atomic_read(&eb->spinning_writers) != 1);
> - atomic_dec(&eb->spinning_writers);
> + WARN_ON(eb->spinning_writers != 1);
> + eb->spinning_writers--;
> }
>
> static void btrfs_assert_no_spinning_writers(struct extent_buffer *eb)
> {
> - WARN_ON(atomic_read(&eb->spinning_writers));
> + WARN_ON(eb->spinning_writers);
> }
IMO longterm it will be good if those debug functions contained
lockdep_assert_held_exclusive/read macros for posterity.
>
> static void btrfs_assert_spinning_readers_get(struct extent_buffer *eb)
> diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
> index 7cb4f1fbe043..c5cc435ed39a 100644
> --- a/fs/btrfs/print-tree.c
> +++ b/fs/btrfs/print-tree.c
> @@ -157,7 +157,7 @@ static void print_eb_refs_lock(struct extent_buffer *eb)
> atomic_read(&eb->read_locks),
> eb->blocking_writers,
> atomic_read(&eb->blocking_readers),
> - atomic_read(&eb->spinning_writers),
> + eb->spinning_writers,
> atomic_read(&eb->spinning_readers),
> eb->lock_owner, current->pid);
> #endif
>
